Field of the Invention
In one of its aspects, the present invention relates to a fluid treatment system. More particularly, the present invention relates to a fluid treatment system for treatment of liquids such as water. Even more particularly, the present invention relates to a fluid treatment system for treatment of water such as ballast water from marine vessels. In another of its aspects, the present invention relates to a method for installing a fluid treatment device in a shipping vessel.
Description of the Prior Art
Fluid treatment systems are generally known in the art. More particularly, ultraviolet (UV) radiation fluid treatment systems are generally known in the art. Early treatment systems comprised a fully enclosed chamber design containing one or more radiation (preferably UV) lamps. Certain problems existed with these earlier designs. These problems were manifested particularly when applied to large open flow treatment systems which are typical of larger scale municipal waste water or potable water treatment plants. Thus, these types of reactors had associated with them the following problems:                relatively high capital cost of reactor;        difficult accessibility to submerged reactor and/or wetted equipment (lamps, sleeve cleaners, etc);        difficulties associated with removal of fouling materials from fluid treatment equipment;        relatively low fluid disinfection efficiency, and/or        full redundancy of equipment was required for maintenance of wetted components (sleeves, lamps and the like).        
The shortcomings in conventional closed reactors led to the development of the so-called “open channel” reactors.
For example, U.S. Pat. Nos. 4,482,809, 4,872,980 and 5,006,244 (all in the name of Maarschalkerweerd and all assigned to the assignee of the present invention and hereinafter referred to as the Maarschalkerweerd #1 Patents) all describe gravity fed fluid treatment systems which employ ultraviolet (UV) radiation.
Such systems include an array of UV lamp modules (e.g., frames) which include several UV lamps each of which are mounted within sleeves which extend between and are supported by a pair of legs which are attached to a cross-piece. The so-supported sleeves (containing the UV lamps) are immersed into a fluid to be treated which is then irradiated as required. The amount of radiation to which the fluid is exposed is determined by the proximity of the fluid to the lamps, the output wattage of the lamps and the flow rate of the fluid past the lamps. Typically, one or more UV sensors may be employed to monitor the UV output of the lamps and the fluid level is typically controlled, to some extent, downstream of the treatment device by means of level gates or the like.
The Maarschalkerweerd #1 Patents teach fluid treatment systems which were characterized by improved ability to extract the equipment from a wetted or submerged state without the need for full equipment redundancy. These designs compartmentalized the lamp arrays into rows and/or columns and were characterized by having the top of the reactor open to provide free-surface flow of fluid in a “top open” channel.
The fluid treatment system taught in the Maarschalkerweerd #1 Patents is characterized by having a free-surface flow of fluid (typically the top fluid surface was not purposely controlled or constrained). Thus, the systems would typically follow the behaviour of open channel hydraulics. Since the design of the system inherently comprised a free-surface flow of fluid, there were constraints on the maximum flow each lamp or lamp array could handle before either one or other hydraulically adjoined arrays would be adversely affected by changes in water elevation. At higher flows or significant changes in the flow, the unrestrained or free-surface flow of fluid would be allowed to change the treatment volume and cross-sectional shape of the fluid flow, thereby rendering the reactor relatively ineffective. Provided that the power to each lamp in the array was relatively low, the subsequent fluid flow per lamp would be relatively low. The concept of a fully open channel fluid treatment system would suffice in these lower lamp power and subsequently lower hydraulically loaded treatment systems. The problem here was that, with less powerful lamps, a relatively large number of lamps was required to treat the same volume of fluid flow. Thus, the inherent cost of the system would be unduly large and/or not competitive with the additional features of automatic lamp sleeve cleaning and large fluid volume treatment systems.
This led to the so-called “semi-enclosed” fluid treatment systems.
U.S. Pat. Nos. 5,418,370, 5,539,210 and Re36,896 (all in the name of Maarschalkerweerd and all assigned to the assignee of the present invention and hereinafter referred to as the Maarschalkerweerd #2 Patents) all describe an improved radiation source module for use in gravity fed fluid treatment systems which employ UV radiation. Generally, the improved radiation source module comprises a radiation source assembly (typically comprising a radiation source and a protective (e.g., quartz) sleeve) sealingly cantilevered from a support member. The support member may further comprise appropriate means to secure the radiation source module in the gravity fed fluid treatment system.
The Maarschalkerweerd #2 Patents are characterized by having a closed surface confining the fluid being treated in the treatment area of the reactor. This closed treatment system had open ends which, in effect, were disposed in an open channel. The submerged or wetted equipment (UV lamps, cleaners and the like) could be extracted using pivoted hinges, sliders and various other devices allowing removal of equipment from the semi-enclosed reactor to the free surfaces.
The fluid treatment system described in the Maarschalkerweerd #2 Patents was typically characterized by relatively short length lamps which were cantilevered to a substantially vertical support arm (i.e., the lamps were supported at one end only). This allowed for pivoting or other extraction of the lamp from the semi-enclosed reactor. These significantly shorter and more powerful lamps inherently are characterized by being less efficient in converting electrical energy to UV energy. The cost associated with the equipment necessary to physically access and support these lamps was significant.
Historically, the fluid treatment modules and systems described in the Maarschalkerweerd #1 and #2 Patents have found widespread application in the field of municipal waste water treatment (i.e., treatment of water that is discharged to a river, pond, lake or other such receiving stream).
In the field of municipal drinking water, it is known to utilize so-called “closed” fluid treatment systems or “pressurized” fluid treatment systems.
Closed fluid treatment devices are known—see, for example, U.S. Pat. No. 5,504,335 (Maarschalkerweerd #3). Maarschalkerweerd #3 teaches a closed fluid treatment device comprising a housing for receiving a flow of fluid. The housing comprises a fluid inlet, a fluid outlet, a fluid treatment zone disposed between the fluid inlet and the fluid outlet, and at least one radiation source module disposed in the fluid treatment zone. The fluid inlet, the fluid outlet and the fluid treatment zone are in a collinear relationship with respect to one another. The at least one radiation source module comprises a radiation source sealably connected to a leg which is sealably mounted to the housing. The radiation source is disposed substantially parallel to the flow of fluid.
U.S. Pat. No. 6,500,346 [Taghipour et al. (Taghipour)] also teaches a closed fluid treatment device, particularly useful for ultraviolet radiation treatment of fluids such as water. The device comprises a housing for receiving a flow of fluid. The housing has a fluid inlet, a fluid outlet, a fluid treatment zone disposed between the fluid inlet and the fluid outlet and at least one radiation source having a longitudinal axis disposed in the fluid treatment zone substantially transverse to a direction of the flow of fluid through the housing. The fluid inlet, the fluid outlet and the fluid treatment zone are arranged substantially collinearly with respect to one another. The fluid inlet has a first opening having: (i) a cross-sectional area less than a cross-sectional area of the fluid treatment zone, and (ii) a largest diameter substantially parallel to the longitudinal axis of the at least one radiation source assembly.
The various embodiments described in the Maarshalkerweerd #1 Patents, the Maarschalkerweerd #2 Patents and the Maarschalkerweerd #3 Patents relate to land-based fluid radiation treatment systems. Typically, the fluid radiation treatment systems are used in conjunction with other treatment systems in the municipal wastewater treatment plant or the municipal drinking water treatment plant, as the case may be. In such installations, various conduit systems and the like are used to interconnect the fluid radiation treatment system to the other fluid treatment systems in the installation.
It is conventional in such installations to compartmentalize each treatment system in the installation such that each treatment system is configured to create its own optimized flow fluid. This approach has been satisfactory for land-based fluid treatment systems.
A problem arises in applications of fluid treatment systems where a very small footprint is available for overall fluid treatment. This problem arises particularly when it is desired to treat ballast water in shipping vessels.
The continuous introduction and spread of aquatic non-indigenous species is a serious threat to the marine environment. Unlike other forms of pollution, once a non-indigenous species establishes itself, it will remain in its new location. While calculating the potential side effects on human food supply, economy, health and overall biodiversity is difficult, there is widespread acceptance that the cost could be staggering.
One primary culprit for introduction and spread of aquatic non-indigenous species is due to unabated transferance of ballast water from shipping vessels. Ballast water taken on in one body of water or ecological zone and released into another body of water or ecological zone can introduce so-called Aquatic Invasive Species (AIS) that has the potential to cause detrimental impact on one or more of the biodiversity, economy and human health of the receiving community.
Typically, a shipping vessel will take on ballast water (fresh water or salt water) and at a source point and hold this in onboard ballast tanks and/or cargo holds to increase stability and maneuverability during transit. Once the shipping vessel arrives at its destination point, the ballast water is typically discharged from the onboard ballast tanks and/or cargo holds. Also, it is common for ballast water to be taken on and/or discharged during transit between the source point and the destination point. It has been estimated that 3-5 billon tonnes of ballast water is transferred in this manner on an annual basis.
International patent application number PCT/CA2010/000701 [Fraser] teaches a fluid treatment system particularly well suited for installation on a shipping vessel for treatment of ballast water. The fluid treatment system comprises a housing within which is disposed a fluid separation section (the separation section may include a single separation device or a combination of two or more similar or disimilar separation devices) and a fluid radiation section in fluid communication with one another. The fluid separation section removes solids in the fluid and the fluid radiation section irradiates the fluid to deactive microorganisms in the fluid. The fluid separation section and the fluid radiation section are configured to have a substantially common fluid flow path which significantly reduces the space or footprint requirement of and/or significantly reduces hydraulic head loss (pressure drops) in the overall fluid treatment system while allowing the two sections to perform their respective functions.
While the fluid treatment system taught by Fraser represents an advance in the art, there is room for improvement. Specifically, the actual embodiments of the fluid treatment system taught by Fraser are focussed on treatment of water during filling of the ballast tanks of the shipping vessel (also referred to herein as “ballasting”). The fluid treatment system taught by Fraser is not focussed on how the system is operated when it is desired to empty the ballast tanks (also referred to herein as “deballasting”)—i.e., the treated water would simply be discharged overboard. However, it would be desirable to have a mode of operation of the fluid treatment system whereby the fluid could be treated to further disinfect it while maintaining the overall efficiency of the system. In addition, there are instances where it is desirable to be able to bypass entirely the fluid treatment system (e.g., in an emergency situation). Further, Fraser is silent with respect to a method for retrofit installation of the fluid treatment system in an existing shipping vessel. These shortcomings are not addressed by the specific embodiments taught by Fraser.
It would be desirable to have a fluid treatment system which addresses the above-mentioned deficiencies of Fraser.